1. Field of the Invention
The present invention relates to a technique to control an ink jet head of an ink jet printer, and particularly to a technique to correct, in an ink jet head including many nozzles, variations in the amounts of droplets discharged from the respective nozzles.
2. Description of the Related Art
An ink jet printer includes an ink jet head. The ink jet head distributes ink supplied from an ink tank into plural pressure chambers, causes pressure to be selectively generated in the respective pressure chambers, and discharges ink droplets from nozzles communicating with the respective pressure chambers. The ink jet printer drives the ink jet head and a recording medium relatively, discharges the ink droplets from the ink jet head, and records an image on the recording medium.
With respect to the ink jet head, according to the discharge method of ink droplets, a Piezo system, a thermal system, an electrostatic system or the like is known.
In recent years, a printer including an ink jet head in which plural nozzles are provided in a line has been developed. Such a printer has a merit that high speed printing can be performed. On the other hand, when the ink jet head is elongated, it is difficult to keep the amounts of droplets as the discharge characteristics of the respective droplets to be uniform by reason of manufacture or material properties. Thus, there is a problem that uneven density occurs in a recorded image and the picture quality is liable to be degraded.
In order to solve the foregoing problem, various techniques are proposed.
A switching device is provided which drives actuator elements arranged correspondingly to plural nozzles individually. The waveforms of voltages supplied to the actuator elements are adjusted, so that variations in the actuator elements are eliminated, and the volumes of discharged ink droplets are made uniform with respect to the respective nozzles (JP-A-2003-170588).
In an ink jet recording apparatus to form an image based on print data, the discharge pattern of ink discharge is selected from plural waveform patterns and printing is performed (JP-A-2005-153378).
Print conditions are previously determined, which include the presence or absence of variation correction of each nozzle, the presence or absence of variation correction of average discharge characteristics of respective groups when plural liquid droplet discharge characteristics are divided into plural groups, and the presence or absence of gradation printing. Further, plural drive waveforms for driving the respective driving elements are determined according to the print conditions. Waveform application means selects the drive waveform according to the print conditions and applies it to the driving element. By this, a reduction in picture quality due to variations in discharge characteristics of droplet nozzles is prevented (JP-A-2006-198902).